Role of bacteriophage T4 baseplate in regulating assembly and infection

Proc Natl Acad Sci U S A. 2016 Mar 8;113(10):2654-9. doi: 10.1073/pnas.1601654113. Epub 2016 Feb 29.


Bacteriophage T4 consists of a head for protecting its genome and a sheathed tail for inserting its genome into a host. The tail terminates with a multiprotein baseplate that changes its conformation from a "high-energy" dome-shaped to a "low-energy" star-shaped structure during infection. Although these two structures represent different minima in the total energy landscape of the baseplate assembly, as the dome-shaped structure readily changes to the star-shaped structure when the virus infects a host bacterium, the dome-shaped structure must have more energy than the star-shaped structure. Here we describe the electron microscopy structure of a 3.3-MDa in vitro-assembled star-shaped baseplate with a resolution of 3.8 Å. This structure, together with other genetic and structural data, shows why the high-energy baseplate is formed in the presence of the central hub and how the baseplate changes to the low-energy structure, via two steps during infection. Thus, the presence of the central hub is required to initiate the assembly of metastable, high-energy structures. If the high-energy structure is formed and stabilized faster than the low-energy structure, there will be insufficient components to assemble the low-energy structure.

Keywords: bacteriophage T4; baseplate assembly; conformational changes; cryo-EM reconstruction; near-atomic resolution.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacteria / virology
  • Bacteriophage T4 / chemistry
  • Bacteriophage T4 / physiology
  • Bacteriophage T4 / ultrastructure*
  • Cryoelectron Microscopy / methods*
  • Crystallography, X-Ray
  • Kinetics
  • Models, Molecular
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Videotape Recording
  • Viral Proteins / chemistry
  • Viral Proteins / ultrastructure
  • Virion / chemistry
  • Virion / physiology
  • Virion / ultrastructure*
  • Virus Assembly*


  • Viral Proteins

Associated data

  • PDB/5HX2